a. Field of the Invention
The invention relates to a fixing structure for an ultra thin rolling bearing for use, for example, in an industrial robot, a machine tool, and medical equipment.
b. Related Art
A gantry bearing in a CT scanner is used as a rotating body bearing provided with an X-ray tube and photographing equipment typically used for image processing. The bearing is an ultra large size device having a bearing outer size of about 1 m and therefore typically coupled to the main body frame of the CT scanner using bolts when it is fixed to the frame.
FIG. 9 shows an example of the CT scanner used as a kind of medical equipment. As shown, in the CT scanner, X-rays generated by an X-ray tube device 50 are directed upon a subject 56 through a wedge filter 52 that equalizes the intensity distribution and a slit 54 that limits the intensity distribution. The X-rays passed through the subject 56 are received at a detector 58 and converted into an electrical signal for transmission to a computer that is not shown. The elements such as the X-ray tube device 50, the wedge filter 52, the slit 54, and the detector 58 are mounted to a rotating base 64 in a substantially cylindrical shape rotatably supported at a fixed base 62 via a bearing 60, and rotated around the subject 56 as the rotating base 64 rotates. In the CT scanner device, the X-ray tube device 50 and the detector 58 opposing each other rotate around the subject 56, so that projection data covering every angle in every aspect in a plane of the subject 56 for examination is obtained, and a tomogram is obtained based on the data using a preprogrammed restructuring program.
The rotating base 64 of the device is coupled to the width side of the rotating ring (hereinafter referred to as “bearing rotating ring”) among the inner and outer rotating rings of the bearing 60. The dominant frequency for vibration resulting from the rotation of the bearing 60 is determined based on the number of bolts or the number of areas fastened with the bolts and the number of revolutions of the bearing 60. Meanwhile, the frame 62 fixed to the non-rotating ring (hereinafter referred to as “bearing fixed ring”) among the inner and outer rings of the bearing 60 tends to have a relatively low natural frequency because the rigidity of the structure is reduced to satisfy a need for a more compact and simple device. Therefore, the frequency of vibration resulting from the rotation of the bearing 60 matches the natural frequency of the structure, and resonance is caused.